Jun 11, 2011

River's roar is mightier than pen

The problem with hydrology is that nobody thinks in terms of flow rates –

50, 100, 400 cubic feet per second doesn’t ring a bell, no matter how accepted the standard, nor does translating it into gallons per minute or acre feet per day.

Rapid in "boisterous" mode: June 2010

Thus my modest proposal:

Let’s convert flow rates into audio equivalents.

Case in point, and custom made for our trail run, is a rapid crevasse in the northern hinterlands of Harford County, Maryland (the place where I grew up) where Deer Creek takes a jagged turn through Rocks State Park.

It consists of a 200 foot run of rapids with a 4 foot waterfall at the end.

You’ll also see from the hydrograph that Rocks is entering into its seasonal “quieting down” mode which in technical hydrologic terms is better known as the summer baseflow recession. Remember, up on the continent spring is the traditional high-water season, not fall as it is in our south Florida swamp.

Currently, Deer Creek is still in “roaring” mode. By summer’s end, however, it should dip into the realm of just clamorous, or maybe even lower depending on how deep into autumn waters continue to fall. Last autumn for example the blaze orange, red and browning leaves fell onto and over a rapid that was – if we look over to the audio vertices on the hydrograph – just rustling.

Very appropriate for the season! As for accuracy ... testing is underway.

During fall the rapid often drops to "rustling" mode, or even quieter

People frequently ask me:

Where would you measure the sound? After all, peak floods would wash away your equipment if you are not careful.

That’s why I recommend taking “audio measurements” of the rapids not from the U.S. Geological Survey’s riverside gauging station which, yes, could be washed away by a flood (i.e., Hurricane Agnes of 1971,) but rather collecting the data from the safe perch of the King and Queen Seat’s outcrop 190 foot high instead.

King and Queen's Seat is the tried and true standard for making
accurate measurements of the rapid's sound.

6 comments:

Rob, What is the sound equivalent of 150,000 cfs that the Missouri River dams in SD are discharging at the moment?We crossed the Missouri yesterday on our way home from MN, the amount of water upstream was incredible.

I like the audio measurement. We visited a local reservoir yesterday. The water level was quite low, all let out in preparation for the expected snowmelt in the next week or so. We could hear the stream flowing into it from across the reservoir, and it was roaring. Audio told the story pretty well. A week of higher temps will bring down lots of water.

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